Railroad tanker cars transport numerous types of fluid cargo. Such tanker cars may include a tank for carrying the fluid cargo and a manway assembly for providing access to the interior of the tank for filling or other purposes. Railroad tanker car manway assemblies of this type may include a nozzle located on the top of the tank for providing access to the tank and a cover for closing the nozzle after filling and during storage and transportation of the tanker car.
A seal may be provided between the nozzle and the cover of the manway assembly to prevent egress of the fluid cargo from the tank and to prevent ingress of dirt and water and other contaminants into the tank. Such seals may be exposed to variations in the chemical composition and physical properties of various fluid cargos. Such seals may also be exposed to variations in mechanical forces during opening and filling through and closing the manway assembly, variations in ambient weather conditions of temperature, wind and moisture, and variations in the pressure differential between the inside and the outside of the tank. During such conditions, the integrity of the manway assembly seal should be maintained and the seal should not leak or otherwise fail.
Railroad tanker car manway assembly seals may be replaced on condition due to leakage or mechanical damage, or may be replaced at appropriate maintenance intervals of time and/or number of open and close cycles of the manway assembly. Seals that have a longer service life interval between replacements and seals that may be replaced with less time are desirable.